1. Field of the Invention
This invention relates to a fit and support system for sports footwear, particularly ski boots, and to footwear utilizing such a system.
2. Description of the Prior Art
Designers of ski boots intended for downhill (alpine) skiing have recognized the need to provide support for the leg, ankle and foot, but have tended to produce boots that are uncomfortable, that do not give the skier proper control, and that restrict those movements of the ankle joint that are necessary during skiing.
Fore and aft movements of the leg at the ankle joint (i.e. plantarflexion and dorsiflexion of the foot) are often restricted or prevented in prior art ski boot by the boot tongue or other structure designed to restrain movements of the foot. Typically, a boot tongue extends from near the toes to the lower shin and, in order to provide good padding and support, is relatively inflexible. Such a tongue presents considerable resistance to dorsiflexion of the foot.
Some boots are designed to permit ankle flexion by pivotally attaching an ankle cuff part to a lower boot part fitting around the foot, without requiring a full length tongue. Such boots, however, as well as being complex and expensive to manufacture, still tend to restrict ankle flexion to some extent and do not provide proper support. Another problem with the known boots is that padding intended to hold the foot firmly tends to produce discomfort without effectively immobilizing the foot, and padding above the ankle often results in uncomfortable chaffing or pinching as well as poor ski control when the ankle is flexed.
Rather than concentrating on providing a new boot design, the inventor has studied ways of overcoming the above problems by providing a fit and support system which can find application in many ski boots of current design, as well as in other types of sports footwear.
It is therefore an object of the invention to provide a sports footwear fit and support system that gives proper support but at the same time allows substantially unrestricted plantarflexion and dorsiflexion of the foot at the ankle joint.
According to one aspect of the invention, there is provided a fit and support system for sports footwear, comprising a lower support shaped and dimensioned to bear evenly against the dorsal surface of the foot, including the medial and lateral aspects thereof, forwardly of the ankle joint, and an upper support shaped and dimensioned to bear evenly against the lower leg at the front above the ankle joint, said supports being capable of independent relative motion to permit unrestricted dorsiflexion of the foot at the ankle joint within the normal range, and said lower support being sufficiently firm to transmit pressure from the footwear to the wearer's foot to substantially reduce articulation of the bones of the mid-foot during use.
According to another aspect of the invention, there is provided a support for sports footwear comprising a body of material shaped and dimensioned to fit within the footwear and to bear evenly against the dorsal surface of the foot, including the medial and lateral aspects thereof, forwardly of the ankle joint, the material being sufficiently firm to transmit pressure from the footwear to the wearer's foot to substantially reduce articulation of the bones of the mid-foot during use without restricting dorsiflexion of the foot at the ankle joint within the normal range.
According to yet another aspect of the invention there is provided a boot assembly for a foot, comprising an outer boot of stiff material having a fastener therefor, and a fit and support system for the boot, said system comprising a lower support shaped and dimensioned to bear against the dorsal surface of the foot, including the lateral and medial aspects thereof, and an upper support shaped and dimensioned to bear against the lower shin at the front above the ankle, said supports being capable of independent relative motion to permit unrestricted dorsiflexion of the foot at the ankle joint within the normal range, and said lower support being sufficiently rigid to transmit force from the boot to the wearer's foot to substantially reduce articulation of the bones of the mid-foot during use.
According to yet another aspect of the invention there is provided sports footwear including a support for the foot, said support comprising a body of material shaped and dimensioned to fit within the footwear and to bear evenly against the dorsal surface of the foot, including the medial and lateral aspects thereof, forwardly of the ankle joint so as not to restrict dorsiflexion of the foot at the ankle joint within the normal range, said material being sufficiently firm to transmit pressure from the footwear to the wearer's foot to substantially reduce articulation of the bones of the mid-foot during use.
The lower support preferably only contacts those parts of the foot necessary to achieve the desired immobilization of the bones of the mid-foot. For example, the support preferably does not contact the toes or the sides of the foot where they curve under to join the sole.
The boot assembly preferably also contains an inner boot of soft material.
The support system of the invention is especially adapted for use with footwear having a substantially rigid foot bed (i.e., combined sole and heel).
The system of the invention applies significant pressure to the dorsal (upper) surface of the foot over the instep, including the lateral and medial aspects thereof, and hence to the bones of the mid-foot, to substantially prevent these bones from moving relative to each other. The term `lateral` is intended to mean the part of the foot on the outside of the mid-sagittal plane of the foot (i.e. the right side of the right foot and the left side of the left foot), and the term `medial` is intended to mean the part of the foot on the inside of the mid-sagittal plane of the foot). The lateral and medial aspects of the dorsal surface of the foot are thus the parts of the upper surface extending on each side of the instep approximately to the position where the upper surface starts to curve under to form the sole of the foot. The pressure in this area tends to make the numerous bones act more like a single bone, or at least reinforces the ligaments and muscles, and also forces these bones against the heel bone to prevent the heel from lifting relative to the bottom of the boot. The pressure applied to the metatarsal bones also maintains these bones in intimate contact with the bottom of the boot.
The lower support preferably loads (i.e. transmits force to) the tarsal bones forward of the ankle joint and the metatarsal bones, from the dorsal or upper surface of the foot, and also sweeps down on each side of the foot to enclose these mid-foot bones and also the forward part of the heel bone, in order to additionally apply lateral and medial loading of these bones.
By shaping the lower part of the tongue to contact the upper surface of the foot evenly and by ensuring that the tongue occupies all of the free space in the boot (when closed) above the foot, evenly applied pressure against the mid-foot bones at right angles to the boot surface can be achieved, rather than generally horizontal pressure on each side of the foot or a generalized crush that many boots provide. The system of the invention thus applies firm pressure to specific areas of the foot and (if necessary) the leg rather than generalized pressure to all parts thereof. Unsupported parts are thus left free for normal movement.
The heel and mid-foot bones form the supportive base for the foot and, by stabilizing these bones relative to each other, the ankle joint becomes almost as stable and strong as the knee or hip joint. By greatly reducing medial and lateral movement of the foot below the ankle joint in this way, ankle wobble is reduced or eliminated and consequently there is no longer any need to support the ankle itself, and thus restrict its movement, by applying lateral and medial pressure against the malleolus (the projection at each side of the ankle joint). Previously, lateral and medial pressure on the ankle bones was considered desirable or essential, but can now be eliminated because ankle joint pronation and supination (lateral and medial bending, such as when the ankle wobbles) is permitted in the main by articulations of the bones below the ankle joint itself, and such articulations are substantially reduced in the present invention.
Despite providing proper support for the foot, the fit and support system allows uninhibited dorsiflexion of the ankle joint within the normal range of motion. In particular, neither the upper support nor the lower support extends into the `crease` of the ankle joint, i.e. the junction between the upper surface of the foot and the front surface of the leg. This leaves the junction clear so that proper flexion of the ankle joint can take place. The upper support is capable of independent relative motion with respect to the lower support and is preferably, but not necessarily, attached to the lower support by a flexible connection. Thus dorsiflexion can take place without interference with the loading applied by the lower support. This is a very important feature of the present invention, at least in its preferred forms, because proper fore and aft balance is a most important feature of ski boot design and when this has been achieved in the past it has usually been done at the expense of ankle freedom.
Although the fit and support system does not restrict ankle flexion, the ski boot itself may do so to some extent. However, this is not usually disadvantageous, provided the ankle can move through the normal range required for skiing and provided the boot applies force evenly and predictably to the skier's leg as the ankle is flexed.
The supports, particularly the lower support, should preferably not be of the "conforming" type, i.e. the type that moulds itself to the shape of the foot when worn, because the loading of the foot achieved by the supports would then be gradually reduced as the shape changed in response to the forces encountered during skiing. Further, supports that are quite flexible, yielding or resilient (e.g. air bladders or the like) are preferably not used because they permit the bones of the foot to move relative to each other and the heel to lift to an undesirable extent. The supports should be made of a firm, relatively unyielding material, e.g., a dense, plastic foam. The surface of such a support may of course be covered by a thin layer of a soft material, such as fabric, for comfort and absorbency.
The supports of the system can be custom fitted by forming and moulding them in place from a polymerizable foam, or other castable material, thus achieving proper conformity with the skier's shin and foot, and ensuring that all free space in the boot adjacent the areas of the foot or leg to be supported is occupied by the tongue.
The flexible connection between the supports used in a preferred form of the invention should allow full freedom at the ankle joint, without any tendency to bind against the lower parts of the leg bones and thus restrict their movement.
In the preferred form of the invention, as indicated above, the fitting and support system employs an upper and a lower support. The lower support can, however, be used alone, for example in sports shoes (e.g. a cycling shoe or a cross-country shoe) rather than boots.
Alternatively, and particularly for ski boots, the system may employ three supports, the third one being an additional upper support, known as a complementary support, that extends around the rear of the lower leg in the same region that the aforementioned upper support extends at the front of the leg. These two upper supports are preferably unconnected, or may be very loosely connected by thin, flexible webbing or the like with sufficient play being present to permit the relative motion of these two supports that is necessary during flexion of the ankle. Together, when the leg is in the upright position, the two upper supports completely encircle the leg in the region where it tapers inwardly above the ankle, and fill all of the voids within the boot that otherwise are present in this region. By eliminating voids in the boot in this way, greater control of movements is achieved, because the boot does not collapse inwardly into internal voids when bending of the ankle takes place, so resistance to bending provided by the boot does not change unpredictably.
During dorsiflexion of the foot, the upper part of a ski boot bears against the shin. For maximum comfort and control, this force should be evenly spread up and down the shin. Conventional tongues tend to concentrate all the pressure at the boot top producing a condition known as shin bite. The upper support of a preferred form of the present invention, however, distributes the pressure evenly because the support exactly follows the movements of the shin and bears evenly against all parts of it. Furthermore, since the upper support preferably does not taper in width towards the ankle joint, the pressure is distibuted over a larger area of the shin than with the conventional boot tongue. The shin is also often curved between the top and bottom of the upper support. If so, the upper support can be shaped to follow this curve on its innermost surface (e.g. by moulding in place) while having a symmetrical outer surface contacting the boot. This also helps to distribute the pressure evenly over the lower shin.
The support(s) forming the fit and support system can be separate from the footwear with which they are used, or can be permanently or removably attached thereto. For example, the supports can be bonded to the inside of a ski boot, boot liner, or the like. The footwear must be such that pressure can be applied to the supports and thus to the foot or leg. However, the way in which this is achieved is not important. For example, a boot or shoe may have a closure formed by toggle fasteners, laces or clamps. Alternatively, the pressure may be applied to the support(s) by a mechanism that is separate from the closure mechanism for the boot or shoe. For example, the support(s) may be drawn against the foot or leg by tensioned straps, cables or plates located within the boot or shoe and not connected to the closure device.